The press ram makes a stroke of 27 in., and its diameter is 30 in., so that at a pres sure of 3 tons per sq. in. (deducting the area of the shank) we have a power of 1,700 tons.
A Forging and Bending Machine, of novel form, made by Williams, White & Co., of Moline, 111., is shown in Fig. 3. The cut shows it as arranged with dies for bending arch bars for freight cars. The machine is a horizontal press, of massive proportions, adapted to be used with a great variety of forms and dies which can be changed at pleasure. The cross-head moves back and forth on the bed. The pitrnans are driven by wrist-pins attached to the main gears, of which there are two—one on each side of the bed. By this method both ends of the cross-head move the same distance in the same time.
Forging Compressed Steel for Guns. Shrifts, ete.—ln order to overcome the want of soundness in steel when cast and forged in large masses. Sir' Joseph Whitworth, at his works near Manchester, Eng., introduced the system of consolidating the steel ingots while fluid under hydraulic pressure, and then forging them on a mandrel by a hydraulic press.
A gradually increasing pressure up to 6 or S tons per sq. in. is applied, and within half an hour or less after the application of the pressure the column of fluid steel is shortened 1,1 in. per foot, or one-eighth of its length; the pressure is then kept on for several hours, the result being that the metal is compressed into a perfectly solid and homogeneous material.
The same system has been recently adopted by the Bethlehem Iron and Steel Works, U. S. A., and by a number of works in England. Open-hearth steel is generally used. The mode of working is thus described by E. H. Carbutt, in his presidential address before the Institution of Mechanical Engineers in /day, 1887 An ingot of the requisite size up to 65 tons is cast either round, or square, or hexagonal, according to the views and experience of each steel maker. The hexagonal form, with sides slightly curved concave, is preferable, because the sides can then follow the shrinkage of the material in cooling, and thus prevent internal rupture of the metal. The ingot, being upright during casting, is cast longer than necessary, so as to get the effect id a head to allow for the steel shrinking as it cools ; the head is afterwards cut off in a lathe. The
ingot in cooling drives the carbon to the center, so that when cold it is found that although the steel on the outside is mild enough for a gun forging, the center is hard enough for tool steel, containing per cent. of carbon. This bard center is then bored out of the ingot, until the test shows that the inside of the annular ring contains the same percentage of carbon as the outside. The center being bored out allows an internal, as well as an exter nal, examination of the ingot. The hydraulic press is then brought into play on the annular ring, with the full advantage of being able to forge on a mandrel. The amount of material which is cut of and bored out of the ingot is so large that it leaves the forging only one-half to two-thirds the weight of the ingot. This loss of material accordingly adds to the cost of the forging.
The hydraulic forging presses vary in power, working at 2,4 to 3 tons pressure per sq. in., and having steel cylinders from 35 to 40 in. diameter, with 4.1 to 71 ft. stroke. In several of them the head which contains the cylinder is movable, so that in forging a large mass the cylinder is lifted up and only a short stroke is necessary. The presses are worked direct by large pumping engines, without the intervention at an accumulator, the engines running only while the press is at work. The cranes all have an arrangement for turning the porter-bar, so that the forging is rotated between the blows of the press. There can be no question that the introduction of the hydraulic forging press has been a great means of overcoming the difficulty of making large steel forging,s. The pressure is so great and so equal throughout that the steel in the center of the ingot is worked at the same rate as the outside ; that is, while an ordinary steam hammer would draw tire outside only and leave the centre un worked, thus bringing about internal strains in the steel, the press acts on the whole mass equally throughout.